The present invention relates to a method for deflecting a flow of reaction gas and for making the part flows formed from the gas turbulent in separate turbulence pipes and for directing them externally to meet a pre-dispersed suspension spray discharging into the reaction chamber, in order to produce a velocity difference, important for reactions, between the particles of the pulverous material and the flow of reaction gas and to shape and control the suspension spray which is being formed.
Two principles are applied to the feeding of a suspension of a reaction gas and a pulverous material into a reaction chamber. According to these principles, the suspension is formed either at a point prior to the actual blast-in device or by means of the blast-in device itself. The former method us used in conventional carbon-dust burners in carbon-dust heating or in metallurgical systems in which a pneumatically carried, finely-divided ore or concentrate, together with its carrier gas, is blown directly into the reaction vessel. When this method is applied, the blast-in velocity must be adjusted so that no blow-back of the reactions can occur.
When high degrees of preheating are used, or in other cases in which the suspension formed is highly reactive, e.g. in the oxygen smelting of a metallurgical sulfide concentrate, the final formation of the suspension must be carried out as close to the reaction chamber as possible, or preferably, as in accordance with the present invention, in the reaction chamber itself.
There are in the literature numerous descriptions of the feeding of a suspension into a reaction chamber. Most of them deal with either direct blowing of a pneumatically carried, finely-divided solid material or systems in which the suspension spray is formed as if in an ejector by means of pressure pulses generated in the reaction gas and blown into the reaction chamber. Such a spray forms a cone with a flare angle of 15.degree.-20.degree. and with the highest concentration of the solid material in the center of the spray. The pattern of the distribution depends mainly on the properties of the solid material and on the flow velocity of the suspension. The solid material and the gas have in this case substantially the same direction.
As known, the transfer of mass between a reacting solid particle and the surrounding gas depends substantially on the velocity difference between them.
It is known and easy to calculate that, within the gas velocity ranges and concentrate particle size ranges normally used in metallurgical apparatuses, the velocity difference between a concentrate particle and the gas tends to be rapidly attenuated. For this reason it is important that the velocity difference between a solid particle and the reaction gas, important for the transfer of mass, is produced or maintained in the reaction chamber at a point where the conditions for the reactions otherwise exist. In cases in which the reacting materials are mixed already at a point prior to the blast-in, the kinetic energy producing the velocity differences is usually at its highest at the blast-in point or a point prior to it. If, on the other hand, the mixing is carried out in the reaction chamber itself, it is possible to adjust the highest velocity difference to be at the desired point in the reaction chamber.
This is so even in a case in which the materials are mixed in part already before they are blasted into the reaction chamber and the final mixing is carried out in the reaction chamber itself.
In several metallurgical processes, such as flash smelting, the reaction gases are directed into a cylindrical, vertical reaction chamber centrally through the top of the reaction chamber via a specific blast-in member, into which the gases are directed horizontally for reasons of space use, etc. This usually results in a one-sided flow in the reaction chamber, since it is difficult to obtain a sufficient length in proportion to the diameter for sufficient control of the blasting in.
Deflection of the reaction gases so as to be parallel to the central axis of the reaction chamber is described in GB patent application No. 2 090 159A. According to this application, the reaction gas is divided into part flows by means of partitions. The part flows are caused to deflect so as to be parallel to the central axis of the reaction chamber in such a way that their velocity simultaneously increases and the part flows discharge into the reaction chamber in such a way that they surround as an uninterrupted curtain the flow of concentrate which is fed from the inside. In the reaction chamber the reaction gas and the concentrate form a controlled suspension spray.
These problems due to a one-sided flow do not appear if the blasting is carried out in accordance with the present invention, since the flow of reaction gas is divided into separate part flows, whereupon the necessary ratio of the cross-sectional area to the conduit length can easily be realized in the flow conduits for the part flow.